The present disclosure describes systems and techniques relating to the configuration of a read channel for a magnetic storage medium.
Signal processing circuits, also called read channels, are frequently used to read storage media and interpret obtained analog signals as discrete values stored on the media. For magnetic storage media, a transducer head may fly on a cushion of air over a magnetic disk surface. The transducer converts magnetic field variations into an analog electrical signal. The analog signal is amplified, converted to a digital signal and interpreted (e.g., using maximum likelihood techniques, such as using a Viterbi detector). Tracking of stored data during a read operation is frequently performed using feedback or decision aided gain and timing control. Additionally, perpendicular magnetic recording techniques can be used to increase the amount of data stored on a magnetic medium.
Various factors can affect the performance of read channels, such as per-unit variability introduced during the manufacturing process or the particular application to which a read channel is applied. The performance of read channels can be evaluated in terms of bit error rates (BER), sector failure rates (SFR), signal to noise ratios (SNR), or combinations of these or other performance metrics.
In order to compensate for at least some of the aforementioned variability, read channels can include many configurable operating parameters that can be tuned to influence the performance metrics (e.g., write pre-comp, analog filter parameters, Viterbi targets, asymmetry correction parameters, equalizer filter taps). One method that is used for configuring such parameters is a linear process, in which one set of parameters is tested to determine a setting that causes the performance metric to most closely approximate a desired result before testing the next set. Full joint optimization is another process that can be used to configure the parameters, in which the values of the parameters are exhaustively scanned to determine a combination of values that causes the performance metric to best approximate a desired result.